Messages in this thread | | | Subject | Re: [PATCH bpf-next v2] selftests/bpf: Switch test_vmlinux to use hrtimer_range_start_ns. | From | Yonghong Song <> | Date | Wed, 1 Jul 2020 11:04:12 -0700 |
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On 7/1/20 10:53 AM, Hao Luo wrote: > The test_vmlinux test uses hrtimer_nanosleep as hook to test tracing > programs. But in a kernel built by clang, which performs more aggresive > inlining, that function gets inlined into its caller SyS_nanosleep. > Therefore, even though fentry and kprobe do hook on the function, > they aren't triggered by the call to nanosleep in the test. > > A possible fix is switching to use a function that is less likely to > be inlined, such as hrtimer_range_start_ns. The EXPORT_SYMBOL functions > shouldn't be inlined based on the description of [1], therefore safe > to use for this test. Also the arguments of this function include the > duration of sleep, therefore suitable for test verification. > > [1] af3b56289be1 time: don't inline EXPORT_SYMBOL functions > > Tested: > In a clang build kernel, before this change, the test fails: > > test_vmlinux:PASS:skel_open 0 nsec > test_vmlinux:PASS:skel_attach 0 nsec > test_vmlinux:PASS:tp 0 nsec > test_vmlinux:PASS:raw_tp 0 nsec > test_vmlinux:PASS:tp_btf 0 nsec > test_vmlinux:FAIL:kprobe not called > test_vmlinux:FAIL:fentry not called > > After switching to hrtimer_range_start_ns, the test passes: > > test_vmlinux:PASS:skel_open 0 nsec > test_vmlinux:PASS:skel_attach 0 nsec > test_vmlinux:PASS:tp 0 nsec > test_vmlinux:PASS:raw_tp 0 nsec > test_vmlinux:PASS:tp_btf 0 nsec > test_vmlinux:PASS:kprobe 0 nsec > test_vmlinux:PASS:fentry 0 nsec > > Signed-off-by: Hao Luo <haoluo@google.com> > Acked-by: Andrii Nakryiko <andriin@fb.com>
Thanks! Acked-by: Yonghong Song <yhs@fb.com>
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